Date: Wed, 28 Nov 2001 14:18:09 -0000 From: "Tariq Rashid" <tariq@inty.net> To: <freebsd-net@freebsd.org> Subject: ip change ? not according to tcpdump. Message-ID: <MPENKFCCIIDAJKJJOLBHAEPOCCAA.tariq@inty.net>
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his post is about an IP address not being reflected "on the wire":
Two freebsd 4.4-release boxes are connected over ethernet via a hub (using
nics at 10Mbs).
The hub is simple in that it doesn't do anything fancy like arp proxying or
caching....
[ A ] ------- ------- [ B ]
| |
[ hub ]
I change the ip address on A as follows:
* ifconfig fxp0 down
* ifconfig 192.168.1.33 (it was 192.168.1.3)
* ifconfig fxp0 up (for good measure!)
now, on A:
* pinging 192.168.1.33 works
* pinging 192.168.1.3 does not -- all good so far
now pinging machine B (ping 192.168.1.1) WORKS :
13:13:48.460568 192.168.1.3 > 192.168.1.1: icmp: echo request
13:13:48.460862 192.168.1.1 > 192.168.1.3: icmp: echo reply
BUT a tcpdump shows pings coming from the old 192.168.1.3 address.
This is a problem as other applications like IKE daemons (isakmpd ported
from openbsd) wants to respond to
the old 192.168.1.3 which isn't there... causing arp requests...
icmp-redirects....
13:13:00.297762 192.168.1.1 > 192.168.1.3: ESP(spi=0x70214267,seq=0x51)
13:13:00.298396 arp who-has 192.168.1.3 tell 192.168.1.33
13:13:00.298468 192.168.1.33 > 192.168.1.1: icmp: redirect 192.168.1.3 to
host 192.168.1.3
Necxt, I tried doing arp -da on both machines... but to no avail: this time
the pings from machine A to B fail with:
13:15:16.914413 192.168.1.3 > 192.168.1.1: icmp: echo request
13:15:17.924035 192.168.1.3 > 192.168.1.1: icmp: echo request
13:15:18.934023 192.168.1.3 > 192.168.1.1: icmp: echo request
13:15:19.944032 192.168.1.3 > 192.168.1.1: icmp: echo request
any ideas anyone?
tariq
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